The war in Ukraine entered a new phase when the Russians called up over 300,000 reserves to commit to the campaign. It coincided with the appointment of Sergey Surovikin as the top commander of the operation. Surovikin is a no nonsense guy known for his aggressive tactics. He was brought in to both restore order to the operation but also change the over all direction of the campaign.
Initially, the Russians assumed that this conflict would quickly end in a negotiated settlement based on the Minsk agreements. The Ukrainians would stop attacking Luhansk and Donetsk and the Russians would stop funding the militias that have been fighting the Ukrainians since 2014. That turned out to be a big mistake on the part of the Russians and they have had to rethink the whole strategy.